Environmental and Molecular Mutagenesis - Legacy Tobacco ...

110 1989 EMS Abstracts 315
http://legacy.library.ucsf.edu/tid/clb93d00/pdf
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INF11JF2KE OF PTA4IID 01 AND EXCISICN RtRAIIt CN THE *IPATICNAL SPECIS3BI . I .B .
Inmbartl, A.J.E. Gatd, B.W. Gliclaaatl2, D .R . MoCalla, 11dcMastet' University,
Namilton, Ontario and 2York University, Toionto, Ontario (Canada) .
1,8-Dinitropyrene is an envizotmental oonRaminar :t MR :id : is mutageni.c in bacteria
and cultured mmuaalian cells, ard aast;inogenic in rodents . This oacpo:atid is
activated in vivo by nitsoraduction to 1-nitxneo-8-nitrvpyrei:e (1,8-NONP), and then
to the hydroxylamine vhich, followinq soet.ylaticn, reacts with D2ZA . The major 17la
adduct fozmed is 1-N-(2'- T :A txatwrrexsions oonsistent with preferential
misinoorporatian of adenine during error pmne bypass of a bulky lesion . Deletions
are detected in all strains, but are itduoed above the spontaneous frequency only
in the e UvrB, p1C+D01 baclognound .
316
M'M(AF2~ 1~1TAGQIESIS ~ RtIE l~I ~ QF~',,,gJi . I .B. Imnbertl, T .A .
Chin1, D .W . Bryant , B .W . Gliclcna~, D.R. MoCalla yMddaster University, Hamilton,
Ontario (Canada) and 2York University, Toronto, Ontario (Canada) .
AF2 is a 5-nitrofaran derivative vhich is :nrtagenic in baateria followitg
activation by endogenas nitx+areduataoes. Pr+avious studies in our laboratory have
suggested that AF2 mrtagenesis is depeneent on the irduction of SOB repair
ftaretiens . In oider to gain greater in4iqht into the mec3 :aaimn by Vhidi AF2 induces,
mutations, we have examined the nutaticnmi specificity of this oaipo :rd in the 11aI
gene of E,gol . Traatment of a ntNrB, P1CU01 host with 1 UM AF2 yielded a nutatian
frequency 300 X that of tastreated oontrols at 20% survival . Mztatiore whicli
occurred in the first 180 base pairs of the episaml JWI gene were ctiaracterized
by L'ta sequenoe analysis . Of the 144 autants in the oollectian, 125 are base
substituticns with trareversicns a :trunberinq txansitions by about 2 to 1 . Ninetytwo
peroent of the base substitutions oaas at G :C beas pairs (62 G :C -> T :A
traneversions, 43 G :C -> A :T transitions, 10 G :C -C :G transveraions) . Base
substitutions ooatr 3 .1 times more frequently at 5'-Pyrimidine-G than 5'-Parine-G
sites . A mec3anism consistent with these results would be the error psnne
imorporation of nucleoti8es across ftnm an apurinic site with an order of
preference of adenine > thymine > guanine . Of the 11 framec+hift mrtatians recovered
in this study, 10 ooour at one hotspot whicA irNolves the loes of the G fraa the
sequence 5'-TTIGCDO-3'
. A further characteriatio of this collection is of several oanplex mutatians irnrolvirg multiple closely spaced ( pn
apart) mrtationnl events .
317
INVITRO DETOXIFICATION OF MX (3-CHLORO-6-(DICHLOROMETHYL)-5-HYDROXY-2-(5H)-F1IRANONE) .
S . Lampelo, T . Vartiainen and S . LSt,jBnen, National Public Health Institute, Dept .
Environm . Hyg . Tox . P .O .B . 95, Kuopio and University of Kuopio, Dept . Chem . P .0 .0 .21,
Kuopio, Finland
MX is a strong bacterial mutagen found in drinking water . In this study the
changes in the mutagenicity of synthesized MX were investigated after its preincubation
with liver 59 (L-S9), human placental S-9 (P-S9), vitamin-C and their combination
utilizing Ames" Salmonella test . The effect of serum albumin on the mutagenicity
of MX was also studied . The etability of MX mutagenicity when diluted in
water and buffer with and without vitamin C was followed during storage at room
temperature .
MX lost its mutagenicity in the presence of P-S9 or L-S9 . Preincubation with vitamin
C (10 ug) enhanced MX mutagenicity whereas adding of P-S9 or L-59 into this mixture
caused a drastic decrease in the mutagenicity . However, no inactivation of the mutogenicity
occurred when P-S9 was incubated with vitamin C before adding MX into thre
mixture . In all cases L-S9 was a very potent inactivator . Albumin decreased the
mutagenicity of MX when added onto the plate but low concentrations of albumin in
the preincubation mixture caused an increase in MX mutagenicity . MX was very stable
when stored in buffered C-vitamine solution whereas it lost its mutagenicity in
water and buffer during two weeks .
These results suggest that inactivation of MX might be due to enzymatic systems but
also to an unspecific binding to proteins . The antioxidents might protect the
reactive genotoxic sites in MX-molecule .
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